A lumbar puncture (or LP, and colloquially known as a spinal tap) is a diagnostic and at times therapeutic medical procedure. Diagnostically it is used to collect cerebrospinal fluid (CSF) to confirm or exclude conditions such asmeningitis and subarachnoid hemorrhage and it may be used in diagnosis of other conditions. Therapeutically it may be used to reduce increased intracranial pressure. Under some circumstances, lumbar puncture cannot be performed safely (e.g. a severe bleeding tendency). It is regarded as a safe procedure, but post-dural-puncture headache is common.
The procedure is typically performed under local anesthesia and aseptic technique. A needle is used to access thesubarachnoid space and fluid collected. Fluid may be sent for biochemical, microbiological, and cytological analysis.
Lumbar puncture was first introduced in 1891 by the German physician Heinrich Quincke.